1. Field
Example embodiments relate to a semiconductor light-emitting device. Other example embodiments relate to a method of manufacturing a vertical semiconductor light-emitting device by a simpler process in which yield is improved.
2. Description of the Related Art
In general, light emitting diodes (LED) may be used to transmit a signal obtained by converting electrical energy into the shape of infra rays, visible rays and/or light using properties of a compound semiconductor. LED may be a type of electroluminescent (EL) devices. LED using a Group III-V compound semiconductor have been used.
Group III nitride-based compound semiconductors may be direct transition type semiconductors. A relatively stable operation may be performed at higher temperatures than in devices using semiconductors other than Group III nitride-based compound semiconductors. The Group III nitride-based compound semiconductors have been used in light-emitting devices (e.g., an LED and/or a laser diode (LD)). Group III nitride-based compound semiconductors may be formed on a substrate formed of sapphire (Al2O3).
FIG. 1 illustrates a conventional semiconductor light-emitting device. Referring to FIG. 1, a lower clad layer 12, an active layer 13 and an upper clad layer 14 may be sequentially formed on a substrate 11 formed of sapphire. An upper electrode layer 15 may be formed on the upper clad layer 14 and a lower electrode layer 16 may be formed on a region of the lower clad layer 12 in which the active layer 13 is not formed. For a GaN-based light-emitting device, the lower clad layer 12 may be formed of n-GaN, the active layer 13 may be formed of a multi quantum wall (MQW) structure of InGaN/GaN, and the upper clad layer 14 may be formed of p-GaN. The upper electrode layer 15 may include a contact layer containing a transparent conductive material (e.g., indium tin oxide (ITO), Ru/Au and/or Ni/Au) and a pad structure containing Au formed on a portion of an upper region of the contact layer. Ti/Al may be used in the lower electrode layer 16.
The lower electrode layer 16 and the upper electrode layer 15 may be formed on one surface of the substrate 11 and may have difficulty applying a potential when a light-emitting surface may be relatively narrow. Because current applied to the active layer 13 through the lower electrode layer 16 may pass through the lower clad layer 12 disposed below the lower electrode layer 16, the structure may not be desirable. A vertical semiconductor light-emitting device may have improved characteristics compared to the above-described horizontal semiconductor light-emitting device illustrated in FIG. 1. Because the substrate may be removed, the lower electrode layer 16 may be formed below the lower clad layer 12. A light-emitting area may be increased and heat dissipation may be more smoothly performed.
FIGS. 2A-2H illustrate a conventional method of manufacturing a vertical semiconductor light-emitting device. Referring to FIG. 2A, an n-GaN buffer layer 124, an InGaN/GaN active layer 126 and a p-GaN contact layer 128 may be sequentially formed on a sapphire substrate 122. Referring to FIG. 2B, trenches 130 may be formed through the p-GaN contact layer 128 exposing the surface of the sapphire substrate 122. The trenches 130 may serve to assist a subsequent chip separation process.
Referring to FIG. 2C, a contact layer 150 may be formed of a material selected from the group including Pt/Au, Pd/Au, Ru/Au and Ni/Au. The contact layer 150 may be formed on the p-GaN contact layer 128. Referring to FIG. 2D, the trenches 130 may be filled with a photoresist (PR) 154. Referring to FIG. 2E, a metal support layer 156 may be formed by applying Cu, Cr, Ni, Au and/or Ag onto the contact layer 150. The metal support layer 156 may be formed by a dicing process. The metal (e.g., Cu) may be relatively ductile and thus, the dicing process may not be easily performed. Referring to FIG. 2F, the sapphire substrate 122 may be removed by irradiating laser light 158 using an excimer laser. Referring to FIG. 2G, the PR 154 may be removed. Referring to FIG. 2H, an n-type ohmic contact layer 160 may be formed on the n-GaN buffer layer 124 using Ti/Al.